Switching between solar panel arrays

[RichardinFrance]

Hello, this is my first post on this forum.

I currently have (or will have in a few days, the panels aren't actually in place yet) a solar array on a west facing roof having 8*375w units. I have a smaller east facing roof on to which I would like to place a second array to get morning sun, however this will not be a match of the first array for the following reasons:

I only have room for 6 panels there.
I would like to use panels of a different type / manufacturer because they have a higher output.

Because I am not very experienced with solar I am looking at how to get these two differing arrays working together. Really, I suppose, I am looking for advice and experience. For example, what is the result of simply paralleling the two arrays, bearing in mind one is 3kw and the other is 2, both with different characteristics?

I have also considered physical switching of arrays but I don't know how my Axpert VMiii inverter will take to that, ie a sudden instantaneous loss of power followed by an immediate restoration....

Any advice?

Thanks

Richard

 

[BentleyJ]

Simple solution,
1) Use an All-in-One type inverter with 2 independent MPPT inputs (1 for each array)
2) Use an AoI inverter with only 1 MPPT input and get a standalone Charge Controller for the other PV array and connect directly to the batteries.
3) Use 2 separate Charge Controllers, 1 for each PV array.

 

[Rocketman]

Does your inverter have two separate mppt channels?

Do you have a battery? - if so the easiest thing may be to put one array just charging the battery with a separate mppt solar charge controller.

To figure out the penalty for combining the arrays we need to know for each array the panels:
Voc
Vmp
Imp
And how many panels on each array.

 

[sunsurfer]

No need to switch them off and on. Likely you will get solar from both arrays at the same time even though they are facing away from each other. This is especially true on those days with diffused light cloud cover.

 

[RichardinFrance]

Does your inverter have two separate mppt channels?

Do you have a battery? - if so the easiest thing may be to put one array just charging the battery with a separate mppt solar charge controller.

To figure out the penalty for combining the arrays we need to know for each array the panels:
Voc
Vmp
Imp
And how many panels on each array.

No unfortunately, only one input, which is the problem to get around.

Yes a battery is present.

East array would be 6 panels Voc 49.8 Vmp 41.3 Imp 8.2
West is 8 x Voc 38.9 Vmp 32.2 Imp 8.76

If you have any useful resources for calculating these things that would be great, I'm not asking anyone to do my homework!

 

[RichardinFrance]

Simple solution,
1) Use an All-in-One type inverter with 2 independent MPPT inputs (1 for each array)
2) Use an AoI inverter with only 1 MPPT input and get a standalone Charge Controller for the other PV array and connect directly to the batteries.
3) Use 2 separate Charge Controllers, 1 for each PV array.

Inverter is Axpert VMiii 4kw with one MPPT input. Thanks for the tips.

 

[Rocketman]

I would get a Victron mppt 250/60 (or 250/70), and wire one of the arrays to it to just charge the batteries. That way both arrays are working at max performance.

If west array 4s2p into it.
If East array 3s2p.

Use the array that most closely matches your 120v usage go into the inverter.

If the west array could handle one more panel you could go 3s3p.

Good Luck

 

[RichardinFrance]

No need to switch them off and on. Likely you will get solar from both arrays at the same time even though they are facing away from each other. This is especially true on those days with diffused light cloud cover.

I think I'm getting it now.

The two arrays would be 1) 257V @b8.76A and 2) 250V @ 8.65A. So one could be providing more current if illuminated but having a fairly closely matched voltage the impact of paralleling the arrays should be minimal....

 

[RichardinFrance]

I would get a Victron mppt 250/60 (or 250/70), and wire one of the arrays to it to just charge the batteries. That way both arrays are working at max performance.

If west array 4s2p into it.
If East array 3s2p.

Use the array that most closely matches your 120v usage go into the inverter.

If the west array could handle one more panel you could go 3s3p.

Good Luck

Thanks, I'll look into that

 

[HalfBaked]

I have 3 arrays E,W,S (5.5kw total) paralleled at the combo box, to one 150/60 mppt. The arrays are positioned so the sun is shaded on one array before the next array picks up. I am working with a small opening in the trees, this works for me.

 

[sunsurfer]

I think I'm getting it now.

The two arrays would be 1) 257V @b8.76A and 2) 250V @ 8.65A. So one could be providing more current if illuminated but having a fairly closely matched voltage the impact of paralleling the arrays should be minimal....

I currently have 7 arrays on one system and 5 on another system. Each string of panels is on their own charge controllers(all Victron). I run lower power strings. I think it's safer and more redundant. My panels are on the ground, kicked up at a slight angle. All are around 60v and all under 1000watts each.

I don't own any AIOs

Solar can be very flexible, you just need to know how it works. I recommend you keep studying and learning.

 

[RichardinFrance]

I currently have 7 arrays on one system and 5 on another system. Each string of panels is on their own charge controllers(all Victron). I run lower power strings. I think it's safer and more redundant. My panels are on the ground, kicked up at a slight angle. All are around 60v and all under 1000watts each.

I don't own any AIOs

Solar can be very flexible, you just need to know how it works. I recommend you keep studying and learning.

Indeed.

I'm going to run with the w array initially. The inverter can handle up to 450v max (it says on the tin!) but I agree, 250vdc @ 10A ish could be a bit tickly.

My electrical theory is good (I'm actually an electrician), it's more a case of not being able to find answers to fairly simple questions, eg what happens when an array is reverse biased. But the answers given here (including yours) are really helpful.

 

[timselectric]

I think I'm getting it now.

The two arrays would be 1) 257V @b8.76A and 2) 250V @ 8.65A. So one could be providing more current if illuminated but having a fairly closely matched voltage the impact of paralleling the arrays should be minimal....

Those voltages and amperages are very close. I would have no concerns paralleling them together.

 

[RichardinFrance]

Those voltages and amperages are very close. I would have no concerns paralleling them together.

This is what I'm thinking.